US20040140581A1 - Exoskeletal leg prosthesis and method for alignment - Google Patents

Abstract

An ankle block for a leg prosthesis comprising an insert having a body with an upper mounting surface and a bottom interface surface opposite from the upper mounting surface. The insert body defines a central coaxial hole therethrough. An over mold is formed about an exterior of the body and extends upwardly therefrom defining a central cavity above the insert and above the upper mounting surface.

Description

BACKGROUND
• The present invention relates to lower leg prostheses and methods of assembly and alignment of lower leg prostheses and more particularly to an improved apparatus and method of assembly and alignment.[0001]
• Traditionally there are two types of lower leg prostheses, an external or exoskeletal apparatus and an internal or endoskeletal apparatus. The exoskeletal apparatus consists of a rigid leg component shaped in the appearance of the external human leg, attached to a foot. Traditionally, the leg component was constructed of solid wood, but now it is more commonly constructed of a resin or lightweight composite material formed around a solid structural foam interior. The composite laminate leg component is extremely lightweight, strong, and capable of supporting very heavy loads. The leg component is attached to the limb of a person through a socket. The,leg component is attached to an artificial foot through a block in the ankle area. The ankle block is usually solid wood or structural foam and contains a fastening mechanism such as a bolt and nut fastener to attach the artificial foot and the ankle block is usually permanently attached to the leg portion through the laminate of the leg component.[0002]
• The method of forming the exoskeletal leg apparatus and aligning the socket and foot for a particular patient traditionally involves an initial bench alignment based on the experience of the prosthetist constructing the apparatus. The alignment of the apparatus is extremely important to the effectiveness and comfort of the finished device. After the leg portion is cast and attached to the ankle block further alignment of this portion is impossible without cutting the cast portion and re-constructing it. The only adjustment easily made by the prosthetist after forming the exoskeletal leg is the minor adjustment of foot rotation made possible through the foot fastener. Thus, due primarily to the alignment difficulty, the modem trend has been away from the exoskeletal leg prosthesis toward a more adjustable endoskeletal leg.[0003]
• The endoskeletal leg apparatus comprises a series of tubes, simulating the bones of the leg, connected via adjustable components to the artificial foot and covered by a cosmetic cover to look like a human leg. The endoskeletal components are traditionally lightweight metals interconnected with fasteners and adjustable components. The advantage of the endoskeletal leg is that all of the components remain adjustable and are easily maintained and replaced if necessary. The components have also been standardized by many manufacturers for easy interchangeability and modularity. The main advantage of the endoskeletal apparatus is the ability for the prosthetist to align the leg by adjusting the components after the leg is statically and dynamically loaded by the end user during a fit test process. The process includes attaching a completely assembled apparatus including a foot to a user and allowing the user to stand and walk on the leg to determine the proper alignment. During this process, minute adjustments are made perfecting the alignment of the leg resulting in a more comfortable and effective prosthesis. The disadvantage of the endoskeletal leg is its relative high cost, its weight, its complexity, its noise potential due to multiple interconnected metal components, its mechanical appearance, and its lower strength capabilities as compared to the exoskeletal apparatus.[0004]
• Thus what is desired is an improved apparatus and method of constructing and aligning an exoskeletal leg prosthesis.[0005]
SUMMARY OF THE INVENTION
• One aspect of the present invention is an ankle block for a leg prosthesis. The ankle block comprises an insert having a body with an upper mounting surface and a bottom interface surface opposite from the upper mounting surface. The insert body defines a central coaxial hole therethrough. An over mold is formed about an exterior of the body and extends upwardly therefrom defining a central cavity above the insert and above the upper mounting surface.[0006]
• Another aspect of the present invention is a method of constructing an exoskeletal leg prosthesis. The method comprises the steps of forming a leg socket for receiving the leg of a user and affixing a temporary adapter to a bottom of the leg socket. An ankle block is attached to the top of a prosthetic wherein the ankle block includes an insert for attaching the block to the foot and an outer mold molded over the insert and having an upwardly extending portion defining a recess therein. A temporary adapter is affixed to an upper surface of the ankle block and an endoskeletal pylon system is attached to the adapters on the ankle block and the leg socket to create a temporary adjustable prosthetic leg. The endoskeletal pylon is adjusted to align the prosthetic foot with respect to the leg socket. After the prosthetic foot is aligned with the leg socket, the prosthetic foot is removed from the ankle block. The adjusted leg is retained in a fixture whereupon the endoskeletal pylon and temporary adapters are removed while maintaining the leg socket and ankle block in their adjusted alignment. A structural foam support is molded between the leg socket and the ankle block and then an outer structural shell is laminated to the combined leg socket, foam support, and ankle block. The prosthetic foot is then reattached to the ankle block.[0007]
• Yet another aspect of the present invention is a method for constructing an exoskeletal prosthetic leg. The method comprises the steps of providing a leg socket and an ankle block affixed to a prosthetic foot. A temporary adjustable endoskeletal pylon is attached between the leg socket and the ankle block. The pylon is adjusted to dynamically align the prosthetic foot with respect to the leg socket. The pylon is adjusted in a dynamic fashion to align the prosthetic foot with respect to the leg socket. The aligned prosthetic leg is then clamped in a fixture and the temporary endoskeletal pylon is removed while maintaining the adjusted alignment of the leg socket with respect to the ankle block. An inner foam core is constructed between the leg socket and the ankle block and a laminated shell is then applied to an exterior of the combined leg socket, foam core, and ankle block.[0008]
• These and other advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims and appended drawings.[0009]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of an exoskeletal leg prosthesis embodying the present invention.[0010]
• FIG. 2 is a perspective view of a prosthetic foot with an ankle block attached thereto and the temporary endoskeletal pylon.[0011]
• FIG. 3 is a cross-section of the prosthetic foot and temporary endoskeletal pylon of FIG. 2.[0012]
• FIG. 4 is an exploded view of the attachment of the prosthetic foot ankle to the temporary endoskeletal pylon.[0013]
• FIG. 5 is a perspective view of an ankle block.[0014]
• FIG. 6 is a cross-section of the ankle block of FIG. 5 and the pyramid adapter tool.[0015]
• FIG. 7 is bottom perspective view of the attachment of the ankle to the ankle block.[0016]
• FIG. 8 is a cross-section of a spacer.[0017]
• FIGS.[0018]9A-J is a stepped sequence of the construction of an exoskeletal leg embodying the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• For purposes of description herein, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in FIGS.[0019]2-3. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
• Turning to the drawings, FIG. 1 shows an exoskeletal[0020]prosthetic leg20 which is one of the preferred embodiments of the present invention and illustrates its various components.Exoskeletal leg prosthesis20 includes aleg portion22 having at an upper portion thereof aleg socket26 defining acavity28 for receiving the leg of a user. Thesocket26 is supported byleg support30.Leg support30 is constructed of astructural foam core34 and further whereinsocket26 andstructural foam core34 are encased in ashell32.Shell32 is typically constructed of a fiber-reinforced resin, or more commonly known as a composite shell, the lay up and construction of which is well known in the art. Afoot portion24 is attached to the bottom ofleg portion22.
• Turning now to FIGS.[0021]2-4, atemporary leg assembly40 is shown whereinfoot portion24 covered byfoot shell38 has anankle block80 attached thereto. A temporaryendoskeletal pylon44 is affixed toankle block80. Temporaryendoskeletal pylon44 comprises anendoskeletal tube50 having atube adapter52 affixed at a bottom thereof and asocket adapter46 affixed at a top thereof.Socket adapter46 is temporarily affixed tosocket26 in a manner that is well known in the art wherebysocket26 has a pyramid portion27 (FIG. 9B) affixed to a bottom thereof which is received insocket adapter46 and retained in place byset screws48 bearing upon individual faces of the pyramid. In this manner, temporaryendoskeletal pylon44 can be retained and adjusted with respect tosocket26 by adjusting setscrews48.
• FIG. 3 discloses a[0022]prosthetic foot36 and attachedankle56. The construction offoot36 andankle56 is similar to the construction of the prosthetic foot assembly disclosed in U.S. Pat. No. 6,129,766, which is hereby incorporated by reference. Further description of thefoot36 and interface withankle56 is not discussed herein.Foot36 andankle56 are received incosmetic foot shell38 to provide the aesthetic appearance of a human foot.Foot shell38 has anupper surface39, which generally defines an opening through which thefoot36 andankle56 are received.Ankle56 differs from the ankle in U.S. Pat. No. 6,129,766 in thatankle56 includes a spherical top attachment surface and atapered attachment hole58 centrally located therein.Tapered bolt insert59 is received inattachment hole58 such that the narrow portion of the taperedinsert59 is oriented toward the top. Afoot bolt60 is inserted through taperedinsert59 andankle56 from the bottom such that the threads ofbolt60 extend upwardly throughankle56 andinsert59.
• An[0023]ankle block80 as shown in FIGS.5-6 is attached toankle56 withfoot bolt60. Referring now to FIGS.5-6,ankle block80 comprises aninsert84 which is typically a machined aluminum structure since a major objective of prosthetic construction is to minimize the weight thereof.Insert84 includes a machined mountingsurface85, which includes four threadedholes86 circumferentially spaced therearound.Insert84 further defines a central hole into which is received a threadedinsert88. Threadedinsert88 can be made from steel or titanium or other sturdy metal for receiving the threaded end offoot bolt60. Thebottom interface surface90 ofinsert84 is spherically concave, the radius of which mates with the spherical radius of theupper surface57 ofankle56. Acircular recess92 is formed in the top ofspherical interface surface90 and analignment pin91 is interferingly received in a hole ininsert84 such that one end ofpin91 extends into the recess defined byspherical interface surface90. The portion ofpin91 that extends intospherical recess90 is received in a like placed recess of spherical mountingsurface57 onankle56 to ensure a desired rotational alignment betweenankle block80 andankle56. Acap89 is affixed over a top end of threadedinsert88 to seal the space aboveinsert84 from the threaded hole ininsert88. Aurethane overmold82 is molded around body81 ofinsert84.Urethane overmold82 is rigid and extends upwardly frominsert84 to form a cup like structure thereby defining a central recess.Notches83 are formed in overmold82 for access as to the central recess for the purpose described below. As seen in FIG. 3, the exterior contour of overmold82 is slightly smaller than the outer perimeter ofupper surface39 offoot shell38. As the final prosthesis is an exoskeletal prosthesis, the slightly smaller periphery of urethane overmold82 from that ofupper surface39 accommodates the thickness of thecomposite shell32 to be formed later, thus providing a smooth transition fromfoot shell38 to the exterior surface ofcomposite shell32.
• Referring to FIGS. 4 and 6, a[0024]pyramid adapter tool94 is placed on mountingsurface85 ofankle block80 and is fastened thereto with four cap screws threaded into threadedholes86 ofinsert84.Pyramid adapter tool94 has at a top thereof apyramid96 with a plurality of pyramid faces97 therearound, which in the present embodiment comprises four pyramid faces.Pyramid adapter tool94 has a sphericalupper surface98 from whichpyramid96 extends at a top center oftool94.
• As seen in FIGS. 3 and 4,[0025]endoskeletal leg44 is affixed topyramid adapter tool94 whereintube adapter52 is received overpyramid96 and setscrews54 are threaded to bear against pyramid faces97. Onesetscrew54 is aligned with each face ofpyramid96. This method of attachingleg44 topyramid96 is the same as the attachment ofsocket adapter46 to the pyramid affixed toleg socket26.
• In use, and as illustrated in FIGS.[0026]9A-J, the prosthetist will, through his experience and expertise, work with the wearer ofprosthetic leg20 in a dynamic manner to adjustfoot portion24 with respect tosocket26 to provide the optimum alignment offoot portion24 with respect tosocket26. The alignment is accomplished by repeated adjustments ofset screws48 to adjustendoskeletal pylon44 with respect tosocket26 and by adjusting setscrews54 intube adapter52 to adjustfoot portion24, includingankle block80, with respect toendoskeletal pylon44 andsocket26.Notches83 formed in the upper portion ofurethane molding82 facilitate the necessary access to setscrews54.
• Once the[0027]foot portion24 has been optimally aligned with leg socket26 (FIGS.9C-D), the prosthesis is removed from the user's leg and inserted into a fixture (FIG. 9E). Fixtures for holding leg prostheses for adjustment and work thereon are well known in the art, and thus specific details are not illustrated herein. The prosthesis is clamped into thefixture18 such that bothfoot portion24 andleg socket26 are individually affixed to the fixture. Once theleg socket26 andfoot24 are retained in their adjusted relationship,endoskeletal pylon44 is removed from betweenleg socket26 and ankle block80 (FIG. 9F). Onceendoskeletal pylon44 has been removed, cap screws95 are removed frompyramid adapter tool94 andpyramid adapter tool94 is removed fromankle block80. Once thepylon44 andtool94 have been removed, a flexibleplastic sleeve100 such as a plastic bag is affixed to a lower portion ofleg socket26 and to the exterior surface of urethane overmold82 ofankle block80. An expandingstructural foam102 is then placed in the bag and allowed to expand and cure. Once the foam has cured, the plastic bag can be removed and the foam core extending from theleg socket26 toankle block80 can be trimmed and shaped to a desired configuration and in a manner known in the art (FIG. 9I). After the structural foam core has been shaped, either in the shape of a human leg or some other desired shape, the fiber reinforcedshell32 is constructed to extend from theupper surface39 offoot shell38 to the top opening ofcavity28 inleg socket26. The construction of the fiber reinforcedshell32 can be accomplished in any of a number of known methods depending upon the type of fiber reinforcement and curable resins utilized to fabricate theshell32. Once the shell has cured, theleg prosthesis20 is ready for use by the wearer wherebyfoot portion24 is reattached (FIG. 9J) and is optimally aligned withleg socket26 with a lightweight composite type construction therebetween and not relying on multiple mechanical interfaces that have the potential to become misaligned, loose, or create undesirable noise.
• When a leg prosthesis such as[0028]prosthesis20 is fabricated for a child, it is also desirable to accommodate for the child's growth without requiring the complete construction of a new prosthesis for every growth increment of the child. To facilitate the growth adjustment for a child, aspacer62 as shown in FIG. 8 is provided.Spacer62 comprises abody69 which has a sphericalupper surface64 and a like sphericalbottom surface65 whereinspherical surfaces64 and65 have the same radius as spherical mountingsurface57 onankle56 and concavespherical interface surface90 inankle block80.Spacer62 includes a raisedcircular boss67 in axial alignment with avertical hole70 through a center ofspacer62.Bottom surface65 also includes an axially centeredcircular recess68 slightly larger in diameter than raisedboss67.Upper surface64 also defines arecess66 proximate to an outer periphery ofspacer62. Analignment pin63 extends frombottom surface65 and is positioned 180 degrees opposite fromrecess66.
• As illustrated in FIG. 7, when the prosthesis needs to be compensated for a child's growth,[0029]foot36 is removed fromankle56 andfoot bolt60 is removed, thus disassemblingankle56 fromankle block80.Spacer62 is placed inconcave recess90 ofankle block80 such thatalignment pin91 is received inalignment recess66 ofspacer62 andankle56 is then mated to the bottom ofspacer62.Boss67 ofspacer62 is received incircular recess92 ofankle block80 to assure axial alignment ofspacer62 withankle block80 andalignment pin63 is received in a corresponding alignment recess inankle56. Alonger foot bolt60 is then inserted from the bottom ofankle56 and threaded intoankle block80 whereuponfoot36 is again reattached toankle56.Spacer62 is typically 0.250 inches in thickness, and up to two spacers can be utilized betweenankle block80 andankle56, thus providing for ½ inch of growth accommodation for a child wearing the prosthesis.
• In the foregoing description those skilled in the art will readily appreciate that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims expressly state otherwise.[0030]

Claims (12)

What is claimed is:

1. An ankle block for a leg prosthesis, said ankle block comprising:

an insert having a body with an upper mounting surface and a bottom interface surface opposite from said upper mounting surface, said insert body defining a central coaxial hole therethrough; and

an overmold formed about an exterior of said body and extending upwardly therefrom defining a central cavity above said insert and said upper mounting surface.

2. The ankle block according toclaim 1 wherein said central coaxial hole has received therein an internally threaded insert.

3. The ankle block according toclaim 2 further including a cap mated to a top of said threaded insert to cover said internally threaded insert:

4. The ankle block according toclaim 1 wherein said overmold is constructed of a molded urethane foam.

5. The ankle block according toclaim 4 wherein said overmold defines at least one notch therein above said insert.

6. The ankle block according toclaim 1 wherein said bottom interface surface in spherically concave and coaxial with said coaxial hole.

7. The ankle block according toclaim 6 wherein said spherically concave surface includes a coaxial circular recess at a top thereof.

8. The ankle block according toclaim 7 further including an alignment pin vertically depending from said spherically concave surface.

9. The ankle block according toclaim 1 further including a removable pyramid tool, affixed to said top mounting surface.

10. The ankle block according toclaim 9 wherein said removable pyramid tool has an upper spherical surface and includes a multi-sided pyramid at a top thereof.

11. A method of constructing an exoskeletal leg prosthesis, said method comprising the steps:

forming a leg socket for receiving the leg of a user therein;

affixing a temporary adapter to a bottom of the leg rocket;

attaching an ankle block to the top of a prosthetic foot, the ankle block including an insert for attaching the block to the foot and an outermold molded over the insert and having an upwardly extending portion defining a recess therein;

affixing a temporary adapter to an upper surface of the ankle block;

attaching an endoskeletal pylon system to the adapters on the ankle block and the leg socket to create a temporary adjustable prosthetic leg;

adjusting the endoskeletal pylon to align the prosthetic foot with the leg socket;

removing the prosthetic foot from the ankle block;

retaining the adjusted leg in a fixture;

removing the endoskeletal pylon and temporary adapters while maintaining the adjusted alignment between the leg socket and the ankle block;

molding a structural foam support between the leg socket and the ankle block;

laminate an outer structural shell to the combined leg socket, foam support, and ankle block;

reattach the prosthetic foot.

12. A method for constructing an exoskeletal prosthetic leg, said method comprising the steps:

providing a leg socket and an ankle block affixed to a prosthetic foot;

attaching a temporary adjustable endoskeletal pylon between the leg socket and the ankle block;

adjusting the pylon to dynamically align the prosthetic foot with respect to the leg socket;

clamping the aligned prosthetic leg in a fixture;

removing the temporary endoskeletal pylon while maintaining the adjusted alignment of the leg socket with respect to the ankle block;

constructing an inner foam core between the leg socket and the ankle block; and

applying a laminated shell to an exterior of the leg socket, the foam core, and the ankle block.

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